DE102013008537A1 - DUAL FUEL COMMON RAIL ENGINE WITH COAXIAL SUPPLY ASSEMBLY - Google Patents

Abstract

A dual fuel common rail engine supplies pressurized natural gas and liquid diesel fuel at different pressures through a coaxial spool assembly for direct injection from a single fuel injector into an engine cylinder. Pressure waves in the gaseous fuel common rail are damped in a coaxial damper-line pressure damping chamber before the pressure wave can interfere with consistent injection rates and gaseous fuel injection rates from the fuel injector.

Description

Technical area

The present disclosure relates generally to dual-fuel common-rail engines and, more particularly, to a coaxial slideway assembly having a gas-pressure damping chamber.

background

Natural gas is increasingly becoming an attractive fuel source option for internal combustion engine applications. One type of natural gas engine ignites a main charge of the natural gas in an engine cylinder by compression ignition of a pilot or premix of diesel fuel. Although a variety of strategies exist to deliver both gaseous and liquid fuels to a compression ignition engine, newer generation engines tend to take advantage of the advantages associated with common rail fuel systems. Additional problems and challenges may be added if there is a desire to adapt a dual fuel system to an existing engine geometry platform. An example of a dual fuel common rail system is in U.S. Patent No. 7,373,931 shown. The present disclosure is directed to one or more of the problems set forth above.

Summary

In one aspect, a dual fuel engine includes a motor housing that defines a plurality of cylinders. A dual fuel common rail system includes precisely one fuel injector positioned for direct injection into each of the plurality of engine cylinders. The system also includes a gaseous fuel common rail and a liquid fuel common rail fluidly connected to each fuel injector, and the system further includes a coaxial jetty assembly with inner and outer tubes in sealing contact a common conical seat of each fuel injection device. The inner tube is out of contact with the outer tube for each coaxial strap assembly. A pressure damping chamber, defined by each coaxial slideway assembly, dampens pressure waves that move from the gaseous fuel common rail to the respective fuel injector. The pressure damping chamber has a larger volume than a volume of the gaseous fuel within the respective fuel injector.

In another aspect, a coaxial dual-fuel common rail fuel rail assembly includes a block that defines a liquid fuel passage that opens through a conical seat into a land conduction chamber and also defines a gaseous fuel passage which opens outside the conical seat into the jetty chamber. An inner tube defines a liquid fuel conduit extending between the second end and the first end with an annular spherical surface resting in contact with, but not connected to, the conical seat of the block. An outer tube has a hollow interior that separates a second end from a first end received in the lead tube chamber. A gaseous fuel conduit extends between an outer surface of the inner tube and an inner surface of the outer tube. An annular seal prevents gaseous fuel from escaping from the gaseous fuel conduit between the block and the outer tube. An upstream half of the gaseous fuel conduit has a pressure damping chamber of greater volume than a volume of a downstream half of the gaseous fuel conduit to dampen pressure waves arriving from the gaseous fuel passage of the block. A boundary line at the second end of the inner tube extends a predetermined target distance beyond a boundary line at the second end of the outer tube so that the inner and outer tubes on a common conical seat in response to a predetermined load on the block along an axis of sitting inside the tube.

In yet another aspect, an operating method for a dual fuel engine includes mounting a dual fuel common rail system to a motor housing. Gaseous fuel is supplied from a common rail for gaseous fuel to each of the plurality of fuel injectors through a respective coaxial slideway assembly. Liquid fuel from a common rail for liquid fuel is also supplied to each of the plurality of fuel injectors through the respective coaxial slideway assembly. Gaseous fuel is injected from a fuel injector into an engine cylinder in response to a gaseous fuel injection signal. Likewise, liquid fuel from the fuel injector is injected into the engine cylinder in response to a liquid fuel injection signal. Variations in gaseous fuel injection rates between the plurality of fuel injectors are provided by damping Pressure waves arriving from the gaseous fuel common rail reduced with a pressure damping chamber, which is defined by the respective coaxial land line assemblies.

Brief description of the drawings

1 FIG. 12 is a schematic view of a dual fuel engine according to the present disclosure; FIG.

2 is a perspective view of a part of the engine and the dual-fuel common rail system of the engine 1 ;

3 is a sectional perspective view of a part of the in 2 shown motor housing to show a structure for a fuel injection device and a motor cylinder;

4 FIG. 4 is a side sectional view through a coaxial slatline assembly according to another aspect of the present disclosure; FIG. and

5 is a partially sectioned side view through a coaxial strap assembly according to another aspect of the present disclosure;

6 , is a partially sectioned side view through a coaxial strap assembly according to yet another aspect of the present disclosure; and

7 is a volume diagram of a gaseous portion of the common rail fuel system for the engine of 1 ,

Detailed description

With initial reference to the 1 - 3 has a dual-fuel engine 10 a dual fuel common rail system 20 on which on a motor housing 11 attached, which is a variety of engine cylinders 12 Are defined. The dual fuel common rail system 20 has exactly one fuel injector 25 for direct injection into each of the plurality of engine cylinders 12 is positioned. A common rail or common pressure line 21 for gaseous fuel and a common rail 22 for liquid fuel are fluid with each fuel injector 25 connected. The dual fuel common rail system 20 also has gas supply and gas pressure control devices 16 as well as liquid supply and fluid pressure control devices 17 , Both the fuel injectors 25 as well as the gas supply and gas pressure control devices 16 as well as the liquid supply and fluid pressure control device 17 are controlled by an electronic engine control device 15 controlled in a known manner. The gas supply and gas pressure control devices 16 may include a pressurized refrigerated cryogenic liquefied gas tank having an outlet fluidly connected to a variable delivery cryogenic pump. The devices 16 may also include a heat exchanger, an accumulator, a gas filter, and a vented fuel conditioning module that controls the supply and pressure of gaseous fuel to the common rail 21 controls for gaseous fuel. The liquid supply and fluid pressure control devices 17 may include a diesel fuel tank, fuel filter and an electronically controlled high pressure fuel pump which supplies liquid fuel to the common rail 22 provide for liquid fuel and control the pressure in it.

How best in the 1 and 2 shown are the blocks 31 the coaxial ridge line assemblies 30 in a row with line segments 18 for gaseous fuel and pipe segments 19 arranged for liquid fuel to the common rail 21 for gaseous fuel or the common rail 22 to define for liquid fuel. The last coaxial condylar arrangement 30 in the series can be a set of plugs or plugs instead of in 2 have shown fittings or fittings.

In addition, with respect to 4 has the dual fuel common rail system 20 also a coaxial bridge line arrangement 30 with an inner tube 32 and an outer tube 33 in sealing contact with a common conical seat 27 from each fuel injector 25 on. In the illustrated embodiment, there is a pressure damping chamber 48 from an upstream segment 49 the line 47 for gaseous fuel having a flow area that is at least several times larger than the downstream segment 50 the line 47 for gaseous fuel. The pressure damping chamber 48 is in each coaxial jetty arrangement 30 Defined to allow pressure waves, which differs from the common rail 21 for gaseous fuel to the respective fuel injector 25 move, be damped, especially during an injection event. The pressure damping chamber 48 has a larger volume than the volume 26 for gaseous fuel (nozzle chamber, SAC and gas passageways) in the respective fuel injection device 25 , Those skilled in the art will recognize that limitations on the available space on the fuel injector 25 the size of the volume 26 for gaseous fuel inside each fuel injector 25 limit. The volume 26 gaseous fuel in each fuel injector may likely be many times less than a nominal gaseous fuel injection volume from the fuel injector 25 ,

A strategy for measuring the pressure damping chamber 48 may begin with the continuity equation and then with deriving an equation for the pressure response of a particular fluid (eg natural gas) in a specific volume (the pressure damping chamber 48 ) to a flow rate that (from the rail 21 ), at a flow rate that leaves the volume (injection rate). The idea is to reduce the pressure swing response to the volume flow of the fluid to a satisfactory level. The pressure damping chamber 48 should provide sufficient absorption of incoming pressure waves to dampen reflective transient behavior. Thus, one could have a maximum nominal volume for the delivery of gaseous fuel for the fuel injector 25 in the engine 10 and consider the gas injection pressure and measure a volume of the pressure damping chamber which will provide sufficient absorption of the pressure waves. 7 shows the relative volume of the common rail 21 for gaseous fuel, the pressure damping chamber 48 and the injector gas volume 26 for the illustrated engine 10 ,

Again with respect to the 2 - 4 can any coaxial condylar arrangement 30 a load or force adjustment bracket 34 with a swivel surface 75 in contact with a block 31 at a load adjustment point 56 have that from the axis 29 of the inner tube 32 is cut. The load adjustment bracket 34 can have a mounting slot 77 and a mounting hole 76 define that a first fastener 81 or a second fastening element 80 take up. The load adjustment bracket 34 pivots at the load adjustment point 56 in response to adjustments of the first and second fasteners 81 . 80 , The fastener 80 may have a spherical washer and a screw while the fastener 81 A screw with a heel that can be used to align the load adjustment bracket 34 adjust. For example, proper assembly may include connection of the coaxial land line assembly 30 with the motor housing 11 with the first fastener 81 require. The screw 80 can then be tightened to a predetermined torque, which is a proper placement of the sealing contact between the outer tube 33 and the inner tube 32 independent, but at the same time, at the common conical seat 27 the fuel injection device 25 ensures. During this process, the load adjustment bracket becomes 34 pan over a certain limited small angle. The fasteners 80 and 81 are in the mounting hole 54 or the mounting slot 55 of the blocks 31 added.

Every block 31 from each coaxial jetty assembly 30 defines a rail passage 45 for gaseous fuel, perpendicular to the axis 29 of the inner tube 32 oriented and fluidly with a passage 46 is connected for gaseous fuel, which at one end in a land line chamber 52 outside the conical seat 53 opens. The rail passage 45 for gaseous fuel can be completely through the block 31 extend to the in the 1 and 2 To allow shown series connection structure. Every block 31 also has a rail passage 42 for liquid fuel extending completely through and perpendicular to the axis 29 oriented and fluidly with a passage 43 connected to liquid fuel, which at one end in the land line chamber 52 through the conical seat 53 opens. A segment of the passage 43 for liquid fuel may be an orifice segment or throttle segment 41 have, as shown, a flow rate from the common rail 22 for liquid fuel to help in transient behavior in the jetty 32 to manage or to control for liquid fuel. The minimum cross section for the orifice or throttle 41 may be calculated by dividing the total injection amount by the duration of injection and by measuring the orifice so as to allow delivery with minimal pressure drop. Thus, the size of the flow area may be related to the performance characteristics of the fuel injector 25 refer or affect. The inner tube 32 defines a line 44 for liquid fuel extending between a first end 60 and a second end 62 extends. The first end 60 has an annular spherical surface 61 which is on a boundary line or contact line in contact with the conical seat 53 rests, and a boundary line on an annular spherical surface at the second end 62 in contact with the common conical seat 27 the fuel injection device 25 , The outer tube 33 has a hollow interior 65 that's a first end 66 from a second end 67 separates. The first end 66 is in the marital chamber 52 taken up, and the outer tube 33 can at the block 31 with matching threads 51 to be appropriate.

Practical manufacturing limitations may include the mass production of coaxial land line assemblies 30 prohibit either the inner tube 32 or the outer tube 33 integral with the block 31 are formed. Thus, an annular seal is used 71 for, against a leakage of gaseous fuel between the block 31 and the outer tube 33 the coaxial bridge line arrangement 30 seal. In this embodiment, the annular seal 71 an o-ring 73 in a face seal configuration that is between the block 31 and the outer tube 33 is captured. In the illustrated construction, the inner tube is 32 at each coaxial catenary arrangement 30 out of contact with the outer tube 33 , A line 47 for gaseous fuel is fluid with the passage 46 connected for gaseous fuel and also extends between the outer surface 63 of the inner tube 32 and the inner surface 69 of the outer tube 33 , Spatial restrictions in the motor housing 11 may require an upstream half 49 the line 47 for gaseous fuel a pressure damping chamber 48 having a larger volume than a volume of a downstream half 50 the line 47 for gaseous fuel. Thus, a major part of the volume of the pressure damping chamber 48 in an upstream half 49 the line 47 for gaseous fuel both inside the outer tube 33 as well as within the marital chamber 52 be located. As previously mentioned, the pressure damping chamber should 48 be of sufficient size and shape to dampen pressure waves coming from the passage 46 arrive for gaseous fuel to reduce variations in injection rates and gaseous fuel injection rates. In this particular example, the available space in the motor housing 11 a relatively uniform wall thickness of the outer tube 33 allow that between an inner surface 69 and an outer surface 68 is defined by two incremental diameter reductions 70 along the axis 29 in a direction of the second end 67 exhibit. Nevertheless, other motor housing geometries may differ significantly from the geometry shown. The rail passage 45 for gaseous fuel from each block 31 can be part of the common rail 22 define for gaseous fuel. The same applies to the rail passage 42 for liquid fuel from each block 31 a segment of the common rail 21 for liquid fuel define how best in the 1 and 2 shown.

With special reference to 4 can be a reliable sealing contact between the coaxial bridging arrangement 30 and the fuel injection device 25 be achieved against leakage of both gaseous and liquid fuels by only a single fastener 80 is attracted to a predetermined torque load. This can be accomplished by placing the boundary at the second end 62 of the inner tube 32 so that they are at a predetermined target distance Δ over the boundary line at the second end 67 of the outer tube 33 extends. The boundary line is the seal contact line. A predetermined load may be on the block 31 through the load adjustment bracket 34 be applied, which along the axis 29 acts, leaving the outer and inner tubes 33 . 32 on the common conical seat 27 sit at their respective boundary lines or contact lines. The accurate control of the predetermined target distance Δ can be achieved in a number of ways. In the illustrated embodiment, the target distance Δ is maintained at a tolerance d, which is an accumulation of a tolerance e, β and α. A dimension distance E +/- of a tolerance e corresponds to the distance between the boundary line of the conical seat 53 and the shoulder or shoulder face against which the O-ring 73 of the block 31 seals. A dimensional distance B +/- a tolerance β corresponds to the distance from the shoulder surface of the outer tube 33 to the boundary line at the second end 67 of the outer tube 33 , A dimensional distance A +/- a tolerance α corresponds to the distance between the boundary lines at the opposite ends of the inner tube 32 , Provided that the distances A, B and E can be kept within reasonable tolerances, the accumulated tolerance d at the desired distance Δ can be made acceptable, so that a proper sealing of the conical seat 27 the fuel injection device 25 is carried out in a reliable manner. The added tolerance or sum tolerance d is equal to e plus β plus α. During pre-assembly, the predetermined target distance D or Δ can be set within an acceptable tolerance e by a block 31 with an appropriate dimension distance E +/- e, further an outer tube 33 with an appropriate dimension distance B +/- β, and by selecting an inner tube 32 with a suitable dimension distance A +/- α. Provided that the sum tolerance of e + B + A gives an acceptable tolerance D, a simple near-foolproof installation can be ensured by simply using a single fastener 80 is tightened with a suitable torque load to a suitable load or force along the center line 29 applied.

To trap dirt, often in fuel flows during the first period of operation of the engine 10 moved freely after it has been built, the coaxial bridging arrangement 30 an edge filter 36 for gaseous fuel and an edge filter 37 for liquid fuel. In the illustrated embodiment, the edge filter 37 for liquid fuel in the pipe 44 be positioned for liquid fuel passing through the inner tube 32 Are defined becomes. The edge filter 36 for gaseous fuel is shown to be within the outer tube 33 between the two step-like diameter reductions or gradations 70 is positioned. In the illustrated embodiment, the edge filter 36 for gaseous fuel have a combined dual purpose by having a holder 38 which can be considered to be in contact with the inner surface 69 of the outer tube 33 and the outer surface 63 of the inner tube 32 is. In this embodiment, the holder 38 having an O-ring that allows gaseous fuel to flow along the conduit 47 for gaseous fuel runs, between the edge filter 36 and the outer tube 33 moved to grime upstream of the fuel injector 25 capture.

Because the inner tube 32 neither on the outer tube 33 still at the block 31 is attached, the coaxial bridging arrangement 30 the holder 38 that is in contact with the outer surface 63 is to the inner tube 32 with the block 31 and the outer tube 33 during handling prior to installation. In other words, the holder 38 can prevent the inner tube 32 from the outer tube 33 falls out during installation before installation. The edge filter 36 /Holder 38 The disclosure allows the coaxial land line assemblies 30 are pre-assembled with a precise predetermined target distance Δ, so that the installation is made simple and simple, without the need for special settings for each coaxial bridging arrangement 30 , In the illustrated embodiment, consistent leak-free installation may only require the fastener 80 to attract to a predetermined load, without any further considerations.

Additionally with respect to the 5 and 6 Two additional embodiments of the coaxial slideway assembly are now shown in which different sealing strategies are used to prevent leakage of gaseous fuel between the block and the outer tube. In particular shows 5 a part of a so-called jetty arrangement 130 in which a disc 135 increased annular sealing webs 136 on opposite sides, which at the block 31 and one end of the outer tube 133 abut when the coaxial bridging arrangement 130 in the engine 10 with the load adjustment bracket 34 is installed as previously discussed. Thus, in this embodiment, the annular seal which leaks gaseous fuel from a location between the block occurs 131 and the outer tube 133 prevents, at the elevated sealing webs 136 on. In addition, this embodiment may be a category part disc 135 use variable thickness, which helps the predetermined predetermined distance Δ for a proper sealing of the second ends of the inner and outer tubes in the common conical seat 27 the fuel injection device 25 to set ( 4 ). 6 shows yet another alternative in which the annular seal, which prevents gaseous fuel between the block 231 and the outer tube 233 by pressing the cone-shaped end 266 of the outer tube 233 against a cone-shaped seat 257 achieved in the block 231 is formed. In each of the alternative coaxial land line assemblies 130 or 230 may be an additional seal or an alternative seal by an annular weld or solder joint between the outer tube 133 and the block 131 be achieved.

Industrial applicability

The present disclosure generally relates to any engine that uses two fluidly separated common rails to provide fuel to a single fuel injector associated with each engine cylinder. The contents of the respective common rails may differ in terms of pressure and / or chemical identity and / or phase or aggregate state without departing from the present disclosure. In the illustrated embodiment, the respective common rails may differ in all three sizes by containing pressurized natural gas and liquid diesel fuel, each at different pressures. The present disclosure finds particular application where a pressure damping chamber is in a coaxial land line arrangement 30 in reducing variations in gaseous fuel injections between a plurality of fuel injectors 25 can help.

Again with respect to the 1 - 4 begins an operating procedure for a dual-fuel engine 10 , that a dual-fuel common rail system 20 on a motor housing 11 is mounted. Gaseous fuel is emitted from the common rail 22 for gaseous fuel to each of the plurality of fuel injectors 25 by a respective coaxial web guide arrangement 30 delivered. Likewise, liquid fuel is from a common rail 21 liquid fuel to each of the plurality of fuel injectors 25 by the same respective coaxial land line assemblies 30 delivered. In operation, gaseous fuel from each fuel injector 25 in an engine cylinder 12 in response to a gaseous fuel injection signal injected, which from the electronic control device 15 to the fuel injector 25 is transmitted. Likewise, liquid fuel from the fuel injector 25 directly into the engine cylinder 12 from the same fuel injector 25 in response to a liquid fuel injection signal from the engine electronic control device 15 injected. Variations of the gaseous fuel injection amounts between the plurality of fuel injectors 25 are reduced by damping of pressure waves coming from the common rail 22 arrive for gaseous fuel, by means of a pressure damping chamber 48 that of each respective coaxial catenary arrangement 30 is defined. During injections of gaseous fuel, gaseous fuel comes in the land pipe chamber 52 from the fuel passage 46 for gaseous fuel. The gaseous fuel then flows into the grooves of the edge filters 36 where dirt is between the outer surface of the edge filter 36 and the inner surface 69 of the outer tube 33 is captured. This flow pattern can be enhanced by providing a suitable geometry which allows the sealing contact between the holder 38 and the various other components that favor the inner tube 32 , the edge filter 36 and the block 31 exhibit. During pre-assembly of each coaxial jetty assembly 30 the predetermined target distance Δ is set as discussed above. One of the strategies discussed (eg, O-ring, raised sealing lands, taper on cone, or annular weld) may be used to prevent leakage of gaseous fuel from a location between the outer pipe 33 and the block 31 seal.

During installation, the inner tube can 32 between the conical seat 53 of the block 31 and the common conical seat 27 the respective fuel injection device 25 be trapped. By using the blocks 31 for each coaxial slideway assembly and by orienting these blocks appropriately as described, the dual-fuel common rail system allows 20 the structure of the common rail 22 for gaseous fuel and the common rail 21 for liquid fuel by series connection of a plurality of coaxial land line assemblies 30 each other using identical line segments 18 for gaseous fuel, pipe segments 19 for liquid fuel and associated fittings or connectors in the respective rail passages 45 for gaseous fuel and rail passages 42 are included for liquid fuel. Both the shown pre-construction and the installation configuration serve to make the inner tube 32 from each coaxial jetty assembly 30 out of contact with the respective outer tube 33 to keep.

The present disclosure addresses a previously unrecognized problem associated with undesirable and possibly unpredictable variations in gaseous fuel injection rates and amounts due to pressure fluctuations within the fuel injector 25 while injection events of gaseous fuel is associated. The present disclosure, in an inventive manner, recognizes that a small flow orifice in the liquid fuel supply prevents the pressure fluctuations in the associated liquid fuel injection variations while a pressure damping chamber 48 with increased volume for a similar purpose in reducing pressure fluctuations during gaseous fuel injection events within the respective fuel injectors 25 serves.

It should be understood that the above description is intended for purposes of illustration only and is not intended to limit the scope of the present disclosure in any way. Thus, those skilled in the art will recognize that other aspects of the disclosure can be obtained from the study of the drawings, the disclosure, and the appended claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 7373931 [0002]

Claims (20)

A coaxial bypass assembly for a dual fuel common rail fuel system, comprising: a block defining a liquid fuel passage which opens into a passageway chamber through a conical seat and defines a gaseous fuel passage opening into the passageway chamber outside the conical seat; an inner tube defining a liquid fuel conduit extending between a first end and a second end, and wherein the first end has an annular spherical surface which rests in, but is not secured to, the contact with the conical seat; an outer tube having a hollow interior which separates a first end from a second end, the first end being received in the land conduction chamber; a gaseous fuel conduit extending between an outer surface of the inner tube and an inner surface of the outer tube; an annular seal adapted to prevent gaseous fuel from escaping from the gaseous fuel conduit between the block and the outer tube; wherein an upstream half of the gaseous fuel conduit has a pressure-damping chamber with a larger volume than a volume of a downstream half of the gaseous fuel conduit to dampen pressure waves arriving from the gaseous fuel passage of the block; and wherein a boundary line at the second end of the inner tube extends a predetermined target distance beyond a boundary line at the second end of the outer tube so that the inner and outer tubes in response to a predetermined load on the block along an axis of the inner tube on a common conical seat sitting. A coaxial bridgework assembly according to claim 1, wherein the annular seal has an O-ring trapped between the outer tube and the block. A co-axial slideway assembly according to claim 1, having at least one holder in contact with an outer surface of the inner tube for holding the inner tube with the block and the outer tube during handling prior to installation. The coaxial slideway assembly of claim 1, wherein the block defines a gaseous fuel rail passage oriented perpendicular to the axis and fluidly connected to the gaseous fuel passage; and wherein the block defines a liquid fuel rail passage oriented perpendicular to the axis and fluidly connected to the liquid fuel passage. A coaxial ribbon guide assembly according to claim 1, comprising a load adjustment bracket having a pivot surface in contact with the block at a load contact point which is cut from the axle; and wherein the load adjustment bracket defines a mounting hole and a mounting slot. A co-axial slideway assembly according to claim 1, wherein the outer surface and the inner surface of the outer tube have two stepped diameter reductions along the axis in a direction of the second end. A coaxial slideway assembly according to claim 6, wherein the annular seal has an O-ring trapped between the outer tube and the block; an edge filter / holder in contact with an outer surface of the inner tube and the inner surface of the outer tube to block dirt and to hold the inner tube with the block and the outer tube during handling prior to installation; the block defining a gaseous fuel rail passage oriented perpendicular to the axis and fluidly connected to the gaseous fuel passage, the block defining a liquid fuel rail passage oriented perpendicular to the axis and fluidic connected to the liquid fuel passage; a load adjustment bracket having a pivot surface in contact with the block at a load contact point cut off the axle; and wherein the load adjustment bracket defines a mounting hole and a mounting slot. A dual fuel engine comprising: a motor housing defining a plurality of cylinders; a dual fuel common rail system, each having exactly one fuel injector positioned for direct injection into each of the plurality of cylinders, a gaseous fuel common rail, and a liquid fuel common rail fluid associated with each fuel injector, and a coaxial ridge assembly having inner and outer tubes in sealing contact with a common conical seat for each fuel injector, the inner tube being out of contact with the outer tube for each coaxial ridge assembly; each coaxial ridge assembly defining a pressure damping chamber to dampen pressure waves traveling from the gaseous fuel common rail to the respective fuel injector; and wherein the pressure damping chamber has a larger volume than a volume of gaseous fuel within the respective fuel injector. The dual fuel engine of claim 8, wherein the coaxial slatline assembly comprises; a block defining a liquid fuel passageway opening into a passageway chamber through a conical seat and defining a gaseous fuel passage opening into the passageway chamber outside the conical seat; wherein the inner tube defines a liquid fuel conduit extending between a first end and a second end, and wherein the first end has an annular spherical surface which is pressed into contact with, but not attached to, the conical seat of the block is; wherein the outer tube has a hollow interior that separates a first end from a second end, and wherein the first end is received in the land conduction chamber; a gaseous fuel conduit extending between an outer surface of the inner tube and an inner surface of the outer tube; an annular seal adapted to prevent gas from escaping from the gaseous fuel conduit between the block and the outer tube; wherein a major part of the volume of the pressure-damping chamber is located in an upstream half of the gaseous fuel conduit; and wherein a boundary line at the second end of the inner tube extends a predetermined target distance beyond a boundary line at the second end of the outer tube so that the inner and outer tubes on the common conical seat in response to a predetermined force on the block along the axis of the inner tube. The dual-fuel engine of claim 9, wherein each coaxial land line assembly includes a load adjustment bracket having a pivot surface in contact with the block at a load adjustment point cut from an axis of the inner pipe; wherein the load adjustment bracket defines a mounting bore and a mounting slot; and wherein the load adjustment bracket pivots at a load adjustment point in response to adjustments to second and first fasteners received in the mounting hole and the mounting slot, respectively. The dual fuel engine of claim 10, wherein the outer surface and the inner surface have two step-like diameter reductions along the axis in a direction of the second end. The dual fuel engine of claim 11, wherein the annular seal has an O-ring trapped between the outer tube and the block; The dual fuel engine of claim 12, wherein each coaxial slatline has a gaseous fuel edge filter and a liquid fuel edge filter. The dual fuel engine of claim 13, wherein a plurality of said blocks are arranged in series with gaseous and liquid fuel lines to define said gaseous fuel common rail and said liquid fuel common rail, respectively; each of the blocks defining a gaseous fuel rail passage oriented perpendicular to the axis defining a portion of the gaseous fuel common rail; and each of the blocks defining a liquid fuel rail passage oriented perpendicular to the axis defining a portion of the liquid fuel common rail. An operating method for a dual fuel engine, comprising the steps of: mounting a dual fuel common rail fuel system to a motor housing; Supplying gaseous fuel from a gaseous fuel common rail to each of a plurality of fuel injectors through a respective coaxial gland assembly; Supplying liquid fuel from a liquid fuel common rail to each of the plurality of fuel injectors through the respective coaxial landline assembly; Injecting gaseous fuel from a fuel injector into an engine cylinder in response to a gaseous fuel injection signal; Injecting liquid fuel from the fuel injector into the engine cylinder in response to a liquid fuel injection signal; and reducing variations in the injection quantities of gaseous fuel between the plurality of fuel injectors by attenuating pressure waves arriving from the gaseous fuel common rail with one Pressure damping chamber, which is defined by the respective coaxial constriction arrangement. The method of claim 15, comprising the steps of: Capturing debris in the gaseous fuel flowing through each respective fuel injector with a first edge filter positioned in a respective one of the coaxial landline assemblies; and Trapping debris in the liquid fuel flowing to each respective fuel injector with a second edge filter positioned in the respective web-line arrangement of the coaxial landline assemblies. The method of claim 16, wherein the assembling step comprises setting a preset target distance between boundary lines at the ends of inner and outer tubes of the coaxial ridge line along a center line. The method of claim 17, wherein the assembling step comprises sealing against leakage of gaseous fuel from a location between the outer tube and the block; and clamping the inner tube between a conical seat of the block and a conical seat of a respective fuel injector. The method of claim 18, wherein the assembling step comprises sequentially arranging a plurality of coaxial land line assemblies to define the gaseous fuel common rail and the liquid fuel common rail. The method of claim 19, wherein the assembling step comprises maintaining the inner tube of each coaxial ridge assembly out of contact with the outer tube of the coaxial ridge assembly.

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